Eizo FS2333 flickering and dim backlight. How to open it?

[Xan03]

Hi everybody,

my 11 year old Eizo FS2333 started having issues today for the first time, the backlight suddenly got very dim and started flickering. I thought that I could run the monitor at 40-50% brightness as a stopgap (100% normally) but even then it flickers a lot. I'm guessing it's failing capacitors on the power board. The boards for this monitor look like this:

https://www.shopjimmy.com/eizo-foris...aming-monitor/
https://www.shopjimmy.com/eizo-foris...aming-monitor/

My guess is that it's the cap next to the regulator on the right. It's only 4 electrolytics on the board so I'd probably just replace all of them. Still a bit disappointing given that they should be Japanese caps in my unit as well and the monitor never really got that warm to the touch. Seems they downsized the cap assortment on that board too much. Anyway, the issue now is that I don't even know how to properly open this thing. After removing all visible screws I still can't get the cover off. Noticed a little empty space under the model number sticker, expecting another screw, but there is just some weird plastic square in there that doesn't seem to be removable. Would be thankful for any suggestions.

[Xan03]

After watching some teardowns of other Eizo monitors, I did manage to take it apart - have to carefully pry the sides open, I used one of those metal tools that are typically used for smartphone displays. Caps on the power board are as follows, and I've also measured all of them in-circuit with an Atlas ESR60:

C002 KXG 100µF/400V (113µF/0.24 Ohms)
C005 KY 10µF/50V (10.35 µF/0.4 Ohms)
C008 KZH 47µF/35V (46.66 µF/0.18 Ohms)
CX01 KZG/KZH/KZN (?) 820µF/25V (900 µF/0.06 Ohms)

So everything looks pretty much in spec, but the CX01 cap that I had originally in mind turned did measure out a bit weirdly - it started out at 1000µF, went down to 900, then I had the idea to gently heat it up just a little bit with a hairdryer, after which it went up to 915µF. ESR could jump from 0.00 to 0.06 or so, but that might be due to to the in-circuit measurement. There is also a seperate board labeled "PCB-DRIVER", which I'm guessing is for the LED backlight, and this has a single poly cap on it, which I don't know what it is but it measured out at 26.4µF/0.32 Ohms. If the 22 on it is supposed to mean 22µF, that seems to be fine.

I'm actually not entirely sure now what model of cap CX01 is, I have written it down as KZG but looking online there is no hint of a 25V KZG, so it might be a KZH or KZN, in which case it seems that a Panasonic FR would be the best replacement that I could get. So unless someone has another idea what else could be causing the issue, I'll just go ahead and replace CX01. In the last days I've noticed that having a fan point towards the monitor seems to lengthen the time until the flicker gets really bad. That to me points to a cap issue as well.

Something else though, I broke the white adhesive on the primary cap while checking, should have perhaps just left it alone. What's a cheap method to stabilize this again, since the industry-grade adhesives seem to go for a lot? Was thinking of some double-sided tape, 3M GPT-020F. Anybody know how strong that stuff is? If it's pretty strong perhaps I'd try to just put it where the adhesive broke, instead of trying to glue to the PCB. It's rated up to 90°C constant.

[Xan03]

Replaced CX01 now, which indeed turned out to be a KZH, with a FR. That KZH measured at 905µF and 0.15 ohms after pulling it, so it was definitely bad. Nominal ESR for that cap is 0.02 ohms. After turning it on, at first the monitor was still very dim and flickered a little bit, but after leaving it on for 20 minutes, it seems to be back to full brightness and no flickering. This to me points to the primary KXG being on its way out too, because after I had unplugged the monitor for a couple days because the flicker was getting intolerable, the cap measured at only 90µF during the repair. I'll just replace this with a KXJ. At that point I think I might as well just do the remaining two electrolytics as well. I can't source an equivalent to KY though, an FC would be the closest but would cut down on the endurance rating a lot. Anybody can tell for sure that putting in an FR in that position would do no harm?

As for the tape, it didn't work at all on the adhesive remaints, but I wound up taping the cap to the PCB and it seemed pretty stable - probably still easy enough to remove when needed, too. So when the other caps arrive I guess I'll see whether that tape holds.

Edit: a minute after typing the post, the monitor did start reducing in brightness and flickering again. By the way, anybody know what these metal "circles" on the yellow side of the PCB are? Are they some metal rings for stabilization purposes, or is that actually just solder?

[Xan03]

Found Nichicon HE as a 1:1 replacement for KY, but ran into an issue with the 47µF/35V KZH cap - this has no FR/FM equivalent and other series like FC, Nichicon PS all have 2.5mm lead spacing instead of 2mm. Closest I can get that fits looks to be a 47µF/25V FR. What are the chances that the cap would actually see >25V in this circuit? Or am I better off just leaving that cap in instead?

[Xan03]

The issue still persists after changing that one cap on the power board, it can be dim for 5 minutes, then bright for a minute and flicker inbetween. So I've looked up what that single poly SMD cap on the sub board is and it's a Nichicon PCV 22µF/63V, rated at 3000h at 105°C. The monitor ran for almost 40,000h as of right now. What are the chances that this cap is what causes the issues with the brightness? The ESR that I have measured on this before (0.32 ohms) would be way out of spec if true, however it was in-circuit and was just a single measurement. The cap does actually appear to be located relatively close to the darkened area on the power board.

A cap with these specs seems to be impossible to get in Europe, as the majority of polys sold are the hybrid types. Importing that capacitor would be quite expensive, so it'd be great to get an opinion on this beforehand.

[Xan03]

This brightness issue seems to actually have some firmware related aspect to it as well. So, the monitor has an "eco" mode that will dim the backlight automatically based on a light sensor. Never used it, so it's always off, but it occurred to me to try and switch it on, and back off again once the brightness issue got really bad. Lo and behold, the backlight got fully bright again, even though the eco mode had not been on in the first place.

Though ultimately I think some worn parts are to blame, because it takes about 10 minutes for it to be dim again and flicker. Maybe there is even some kind of connection to what's displayed on screeen, as in, dark content might cause it to dim even more. Perhaps worn enough caps cause the firmware to go haywire in some ways.

[CapLeaker]

This brightness issue seems to actually have some firmware related aspect to it as well. So, the monitor has an "eco" mode that will dim the backlight automatically based on a light sensor. Never used it, so it's always off, but it occurred to me to try and switch it on, and back off again once the brightness issue got really bad. Lo and behold, the backlight got fully bright again

??? Did the backlight flicker when on full tilt? Look if something white is displayed on the LCD has a pinkish hue.

[Xan03]

I'm not seeing any color issues, just the backlight goes dim soon after turning on, and eventually starts flickering. It doesn't really flicker in the rare case where it still runs at 100%, but I've seen it run at about 50% and then flash to 100% for a brief moment, which looks really bad.

[CapLeaker]

I think you are replacing caps and that isn't the issue here. My bet is either a cold solder joint somewhere or bad backlight LED's, just finding it is another story. Turn up the backlight manually to full tilt and see how long the backlights stay on.

[Xan03]

A cold solder joint I doubt, because moving the monitor around has no bearing on the issue. It wasn't moved either when the issue started.

Bad LEDs I have considered and that could be a possibility, but I have no way of diagnosing or fixing that as it would involve disassembling the panel itself. Though I've read that these LEDs should be more durable than CCFLs.

Putting the brightness at 100% (which is what I used to run for the longest time), it will stay at an actual 100% only for very few minutes until the issues start. I'm running right now at 70% with a fan towards it, which seems to help to at least prevent the flicker for a while. So because the issue is time and probably heat related, I'm suspecting caps. The cap that I pulled also fluctuated and read out with a high ESR, and the primary cap also fluctuated. I think even though the measurements might not be perfect, there shouldn't be such high capacitance fluctuations. Doing the rest of the power board wouldn't be a big issue, the question for me is whether it's worth doing the single poly cap.

[Xan03]

Well, I'll order a new primary cap and put that in, and hope that fixes the problem and I won't have to mess with the SMD cap. Will upgrade to 450V as well. If you look at the power board, it actually has space for two primary caps, and the one that they used only takes up about 4/5 of the footprint. That smells like cost cutting to me, though on the other hand I don't understand why they used a 63V part for that poly cap on the driver board.

[stj]

the 2 caps may be a voltage-doubler design for the u.s. market

[Xan03]

It should be multi voltage capable. Manual says this:

100 - 120 VAC ±10 %, 50/60 Hz 0,7 A
200 - 240 VAC ±10 %, 50/60 Hz 0,45 A

[CapLeaker]

I've seen some weird cold solder joints, that were are real head scratcher and that thing ran for 20 years before without hiccups. Did you try heating or cooling (can of air upside down) and see what happens?

[Xan03]

Well, I didn't apply heat, but use a fan due to summertime. The thing is, when it dims or flickers, it's always completely uniform across the screen. At least from what I can imagine, a cold solder joint could show as either some individual LED failing, or a more severe failure than what I'm seeing. And it would probably be affected by applying some vibration, which this is not. It's just affected by letting the monitor run - the longer it runs, the dimmer and more flickery it gets, and setting the brightness high accelerates it. On brightness set to 100%, after turning the monitor on, it will run for 20 minutes until it starts getting really bad. Then I turn the fan on, just towards the screen side, and the flicker goes away quickly for the moment. But only setting the brightness down to 70% will really help the flicker, though this outputs really at 40% or something in reality.

My guess is still that the caps went bad after 11 years, because as seen by that PCB discoloration, that power board must get quite hot. The metal enclosure isn't perforated and probably traps the heat really well, so from touching the monitor you would never know. Actually might be a not so great design. The KZH cap that I pulled measures with +10% capacitance, so presumably high leakage current, and ESR that starts out at 0.02 ohms, then 0.04 on the next time and so on, until it hits 0.15 and even 0.2 ohms. So IMO at least that cap is verifiably bad. It was also pretty much right in the hotspot.

I just don't know if that poly cap that apparently filters the power to the panel and/or LEDs went bad. But judging by another thread here apparently those LEDs might actually run at near 63V, which I didn't know.

[CapLeaker]

I wasn't talking about the LEDs in the backlight. And even in that case the problem would be affecting only one LED string, unless there is only one LED string. Caps I am not convinced that they are the problem. My reasoning is, you should have the problem in reverse, like a hard start or flickering when cold. I would gun for the opposite like whatever is getting hot. Cold solder joints do not have to be under vibration for that to happen. They can happen because of use just by heating up and cooling down again.
Now if you put wifeys hair dryer to it, you could heat up the board and see if it fails faster, then only heat a sections… etc.

[Xan03]

A cold solder joint would have to exclusively affect the power delivery to the LEDs in some way, because the image is fine otherwise. But a joint can only have two states, connected or not connected, so I would assume it to alternate between fail/not fail, but it's actually much more granular. First it dims, then flicker starts etc. When running 70% with a fan, it can run for a good while without flickering while further dimming gradually over time. So that granularity is why I'm thinking component failure rather than cold solder joint. You could say it's several cold solder joints but that would be unlikely as the issue started suddenly and didn't really change. Well, I'm not a pro, so I'm open to being told this is wrong reasoning though.

The primary cap measured 113µF right after the monitor was on, but only 90µF after it was off for a couple days. That is a large difference in leaking current. So my hope right now is the issue is caused by a bad primary cap - low µF compared to other monitors+heat+APFC. But my suspicion is just as much on that poly cap, because that driver PCB is more specific to the backlight.

[Xan03]

Haven't done anything else so far, but the issue actually improved since, at least in my perception. Almost no flicker, still getting progressively dimmer over the day but it can run for hours with decent brightness now. Been running with it set to 100% again this entire week. The only thing that changed is maybe a 1-2°C higher room temp.

What I haven't mentioned is the cap I put in was actually over 4.5 years old according to the date code and measured with out of spec ESR, so maybe it reformed in circuit and is working better now, but I have no idea if that could take days as opposed to hours. And yes, that's a part I ordered as new as opposed to something I had just lying around.

[Xan03]

Replaced the primary power cap today, and that changed absolutely nothing, which I already expected after pulling the old cap and measuring both. The new one actually measured with ever so slightly lower capacitance and higher ESR, despite being a bit longer. So the old primary cap was probably fine, though I still don't understand the capacitance fluctuations that I saw on it.

I'm really looking at the poly cap next, because it measured with an ESR of 0.44 ohms, while the spec sheet says either 37 milliohms (8x10) or 56 milliohms (10x8) for this - I think the latter dimensions should be correct. And, again, that sub-board should be directly responsible for driving the backlight. Though it's an in-circuit measurement, and I find it hard to believe that a poly cap would age this badly. If it really does turn out to be this cap, it would perhaps mean they selected a part with too little capacitance, and you could call that a case of planned obsolescence right there.

[CapLeaker]

Maybe post a picture of that sub board?